Tissue factor pathway inhibitor (TFPI) is 276 amino acids in length and functions as an inhibitor of tissue factor-mediated blood coagulation. See U.S. Pat. No. 4,966,852. The amino terminal end of TFPI is negatively charged, and the carboxy terminal end is positively charged. The TFPI protein contains three Kunitz-type enzyme inhibitor domains. TFPI contains 18 cysteine residues and forms 9 disulfide bridges when correctly folded. The primary sequence contains three N-linked consensus glycosylation sites (Asn-X-Ser/Thr). The asparagine residues of the glycosylation sites are located at positions 145, 195 and 256. TFPI is also known as lipoprotein associated coagulation inhibitor (LACI), tissue factor inhibitor (TFI), and extrinsic pathway inhibitor (EPI).
Use of TFPI has been proposed for the treatment of various indications, including sepsis (U.S. Pat. No. 6,063,764 and WO 93/24143), deep vein thrombosis (U.S. Pat. No. 5,563,123, U.S. Pat. No. 5,589,359, and WO 96/04378), ischemia (U.S. Pat. No. 5,885,781, U.S. Pat. No. 6,242,414, and WO 96/40224), restenosis (U.S. Pat. No. 5,824,644 and WO 96/01649), and cancer (U.S. Pat. No. 5,902,582 and WO 97/09063). A TFPI variant, which differs from TFPI by the addition of an alanine residue at the amino terminus (“ala-TFPI”), has been shown to be efficacious in animal models for the treatment of sepsis. Carr et al., Circ. Shock 44(3), 126-37, 1994.
There is a continuing need in the art for biologically active, purified TFPI and methods of obtaining it.